The major goal of these projects is to study the mechanisms of neutrophil motility. This is done by mechanically characterizing the three major components of cell motility: adhesion, cortical rearrangement and cell body contraction, and by characterizing the signaling of a variety of motility responses, such as pseudopod formation, locomotion, and release of free cytosolic calcium. The experimental techniques used are micropipet manipulation combined with video microscopy and also a new micropipet technique called the biointerface probe. This technique can be used to measure single molecular adhesive bond strengths, as well as to probe cell surface topography and cortical tension. During the past year, we have measured the cortical tension of the resting neutrophil and are continuing to perform these experiments upon stimulation by agents that are known to affect the stiffness of the sub-surface cortical layer,beginning with fMLP and cytochalasin D. We have also examined the effects of cytosolic calcium on the neutrophil motility response. Our plans are to continue these experiments and also to begin making measurements of adhesion molecule bond strengths, with emphasis on L- selectin. In this work, we use human neutrophils from veinous blood as well as cells from finger pricks. These cells will be used for the entire duration of the grants. The total number of blood donors is expected to be in the range of 20 to 30. This is not a multi-center project or a clinical trial.